This project will compare the protein sequences of myosins I with each otherand with myosins II and other related proteins to identify and localize functional domains within the myosin I molecules. The myosins I are a recently discovered class of proteins that have myosin II-like head domains, but unique, non-helical tail domains. Comparisons will focus on the brush border myosins I from intestinal epithelial cells from chicken and cow, which are the only vertebrate myosins I to be isolated and biochemically characterized, but the rapidly accumulating number of myosins I from other sources will also be included in the comparisons.